Configuration Variations For Standard Ha Pair Configurations; Preferred Practices For Ha Pair Configurations - IBM N Series Hardware Manual

Consider the following questions about your installation before proceeding through the setup
program:
Do you want to configure VIFs for your network interfaces?
How do you want to configure your interfaces for takeover?
Attention: Use VIFs with HA pairs to reduce SPOFs (single points of failure). If you do not
want to configure your network for use in an HA pair when you run setup for the first time,
you can configure it later. You can do so either by running setup again, or by using the
ifconfig command and editing the /etc/rc file manually. However, you must provide at
least one local IP address to exit setup.

7.3.1 Configuration variations for standard HA pair configurations

The following list describes configuration variations that are supported for standard HA pair
configurations:
Asymmetrical configurations: In an asymmetrical standard HA pair configuration, one
node has more storage than the other. This configuration is supported if neither node
exceeds the maximum capacity limit for the node.
Active/passive configurations: In this configuration, the passive node has only a root
volume. The active node has all the remaining storage and services all data requests
during normal operation. The passive node responds to data requests only if it takes over
for the active node.
Shared loops or stacks: If your standard HA pair configuration is using software-based
disk ownership, you can share a loop or stack between the two nodes. This is useful for
active/passive configurations.
Multipath storage: Multipath storage for HA pair configurations provides a redundant
connection from each node to every disk. It can prevent some types of failovers.

7.3.2 Preferred practices for HA pair configurations

Follow these preferred practices to ensure that HA pair storage systems achieve maximum
uptime:
Make sure that the HA pair storage systems and shelves are on separate power supplies
or grids. This configuration prevents a single power outage from affecting both controller
units and shelves.
Use VIFs to provide redundancy and improve the availability of network communication.
The virtual interfaces are set up during initial installation or the subsequent initiation of
setup.
Maintain a consistent configuration between HA pair nodes (such as Data ONTAP
versions). An inconsistent HA pair storage system configuration is often related to failover
problems.
Test the failover capability periodically (for example, during planned maintenance) to
ensure an effective HA pair storage system configuration.
Follow the documented procedures in the upgrade guide when upgrading HA pair storage
systems.
Make sure that HA pair nodes have sufficient resources to adequately support workload
during takeover mode.
Periodically use the HA pair configurations checker to help ensure that failovers are
successful.
Chapter 7. Highly Available controller pairs
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